Relapse to drug use following periods of abstinence is a significant impediment in the long-term treatment of cocaine dependence. Environmental stimuli or contexts previously associated with drug use or priming doses of the abused drug can initiate relapse to compulsive drug-seeking and drug-taking behaviors. The Animal Core B will provide all of the experimental subjects for every project in the Neurobiology of Addiction Research Center (NARC) that involves the use of the self-administration and relapse model in rats. Rats will be catheterized and trained to self-administer intravenous (i.v.) cocaine using standard schedules of drug reinforcement. After a stable period of self-administration, lever pressing for drug will be extinguished to criterion, or animals may undergo abstinence. Subjects will then be directed towards individual NARC projects for brain tissue extraction, electrophysiology, or assessment of behavioral responding to systemic or site directed manipulations in accordance with the specific aims of each NARC project. The aims of Animal Core B can be summarized as: 1. Provide experimental subjects to all projects in the NARC that are consistent and satisfy specific criteria with regards to experience in drug self-administration and in the degree of withdrawal, extinction, and/or abstinence. The Animal Core will insure that subjects will be handled and treated according to all approved animal use procedures and, in conjunction with vivarium staff, maintain appropriate animal husbandry. 2. Efficiently manage the distribution of animals to the different projects to insure that statistically relevant group sizes and group replications are made available to each project in a timely manner. 3. Maintain a staff of well-trained technicians to efficiently generate experimental subjects using a balanced group design, as well as provide technical assistance to NARC Projects that will involve further behavioral evaluation of drug-seeking behavior. 4. Serve as a NARC training center for junior investigators who desire training in self-administration, jugular catheterization, operant conditioning methods, and other related experimental procedures. The NARC Animal Core will serve as the common foundation for all NARC projects. The results from integrated studies through the Animal Core will hopefully lead to useful pharmacotherapeutic agents for the treatment of cocaine abuse and dependence.